Fetal Ultrasound

Test Overview

Fetal ultrasound is a test done during pregnancy that uses
reflected sound waves. It produces a picture of the baby (fetus), the organ that supports the fetus (placenta), and the liquid that surrounds the fetus
(amniotic fluid). The picture is displayed on a TV
screen. It may be in black and white or in color. The pictures are also called
a sonogram, an echogram, or a scan. They may be saved as part of your baby's
record.

Fetal ultrasound can be done two ways. In a transabdominal ultrasound, a small handheld device called a transducer is moved over your belly.
In a transvaginal ultrasound, a transducer is put into your vagina.

Fetal ultrasound is the safest way to check for problems
and get details about your fetus. It can find things such as the size and position of the fetus. It does
not use
X-rays or other types of radiation that may harm your
fetus. It can be done as early as the 5th week of pregnancy. Sometimes the sex of your
fetus can be seen by about the 18th week of pregnancy.

Ultrasound is one of the screening tests that may be done in the first
trimester to look for
birth defects, such as Down syndrome. The
first-trimester screening test uses ultrasound to measure the
thickness of the skin at the back of the baby's neck. This screening also includes blood tests that measure the levels of two substances that may be related to birth defects.

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Look at the size and position of the fetus, placenta, and
amniotic fluid.

Check the position of the fetus,
umbilical cord, and placenta during a procedure such as
amniocentesis or umbilical cord blood
sampling.

Find major birth defects, such as a neural tube defect
or heart problems.

3rd-trimester fetal
ultrasound is done to:

Make sure that a fetus is alive and
moving.

Look at the size and position of the fetus, placenta, and
amniotic fluid.

Transvaginal ultrasound is most often done early in a
pregnancy to check the age of the fetus. It may also be done if your doctor thinks you may have an
ectopic pregnancy. It is sometimes done late in
pregnancy to find the location of the placenta. And it may be done in a high-risk pregnancy
to check the length of the
cervix.

How To Prepare

You may need a full
bladder for the test. If so, you will be
asked to drink water or other liquids just before the test. You will be asked not to urinate before or during the test. In most cases, women in the third trimester do not need to have a full bladder.

For a
transvaginal fetal ultrasound, the vaginal transducer is usually covered with a
latex sleeve and a lubricant, such as K-Y Jelly. If you are allergic to
latex, tell the health professional before you have the test.

Talk
to your doctor if you have any concerns about the need for the ultrasound, its risks, how it will be done, or what the results will mean. To
help you understand the importance of this test, fill out the
medical test information form(What is a PDF document?).

How It Is Done

Most often, a fetal ultrasound is
done by an ultrasound technologist. But it may be done by a
radiologist or
obstetrician. Fetal ultrasound can be done in a
doctor's office, hospital, or clinic.

You may not need to remove
your clothes for this test. You can lift your shirt and push down your skirt or pants. If you are wearing a dress, you will get
a cloth or paper covering to use during the test.

Transabdominal ultrasound

You may need to have a full
bladder. A full bladder helps transmit sound waves, and
it pushes the intestines out of the way of the uterus. This makes the ultrasound
picture clearer.

You will not be able to urinate until the
test is over. But tell the ultrasound tech if your bladder is so full
that you are in pain.

If an ultrasound is done during the later part of
pregnancy, a full bladder may not be needed. The growing fetus will push the
intestines out of the way.

You will lie on your back on an exam table. If you become short of breath or feel faint while lying on
your back, your upper body may be raised or you may be turned on your side.

A gel will be spread on your belly.

A small, handheld
device called a transducer will be pressed against the gel on your skin. It will be
moved across your belly several times. You may watch the monitor to see the
picture of the fetus during the test.

The test takes about 30 to 60 minutes. When it is finished, the gel is cleaned off your
skin. You can urinate as soon as the test is done.

Ultrasound techs are trained
to gather images of your fetus. But they can't tell you if it looks normal or
not. Your doctor will share this information with you after the
ultrasound images have been reviewed by a radiologist or
perinatologist.

Transvaginal ultrasound

You do not need to have a full
bladder.

You will lie on your back with your hips slightly
raised.

A cover (such as a condom) will be placed over the thin
transducer. The transducer will be put gently into your vagina. It will be moved to adjust the image on the
monitor. Some doctors may let you to put the transducer into your vagina
yourself.

This test takes about 15 to 30
minutes.

How It Feels

During a transabdominal ultrasound, you
may have a feeling of pressure in your bladder. The gel may feel cool when it
is first put on your belly. You will feel a light pressure when the
transducer is passed over your belly.

Normally a transvaginal ultrasound does not cause discomfort. You may feel a light
pressure when the transducer is moved in your vagina.

Risks

There are no known risks linked with a fetal
ultrasound, either to the mother or fetus.

"Keepsake video operations" are ultrasound centers that sell ultrasound videos
as your baby's first photo. The U.S. Food and Drug Administration (FDA) does not recommend ultrasounds for this reason. It recommends ultrasounds only to obtain medical information about a fetus. Keepsake centers may use the ultrasound machine at higher energy
levels and for longer times than needed in order to get a "good picture."

Results

Fetal ultrasound is a test done during pregnancy that uses
reflected sound waves. It produces a picture of the baby (fetus), the organ that supports the fetus (placenta), and the liquid that surrounds the fetus
(amniotic fluid).

You may not get details about the test right away. Full results are usually available in 1
or 2 days.

Fetal ultrasound

Normal:

The fetus is the size expected for its
age.

The heart rate and breathing are normal
for the age of the fetus.

If the test is done late in the pregnancy, the fetus
is in the head-down position.

The placenta is the size expected for
the stage of the pregnancy.

The
uterus has the right amount of amniotic fluid.

No birth
defects can be seen. (Many minor defects and some major defects are not easy to see. Also, birth defects do not always show up early in pregnancy.)

Abnormal:

The fetus is growing more slowly than
normal, is small, or is less developed than it should be for its age.

The fetus is
abnormally large for its age.

If this test is done late in the
pregnancy, the fetus is in the buttocks-down
(breech) position.

Many conditions can affect fetal ultrasound results. Your
doctor will discuss any abnormal results with you in
relation to your past health.

What Affects the Test

You may not be able to have the test, or the results may not be helpful, if:

You are very overweight.

You have stool (feces) or air in your
intestines or rectum.

You have an abnormally low amount of amniotic
fluid.

Your fetus is in certain positions.

You are not able to lie
still during the test.

The fetus is very active.

What To Think About

Fetal ultrasounds do not always show birth
defects. Normal ultrasound results can't guarantee that your baby will be healthy. No test can do that.

Your doctor may suggest
more tests if the results of your fetal ultrasound are not
normal.

A photograph or videotape of the ultrasound
image of the fetus may be offered to you.

Your due
date may be changed based on an ultrasound done in early pregnancy. The
ultrasound may predict a different date, based on fetal size and
development.

In the third
trimester, fetal ultrasound may not find the exact fetal age or weight.

The effects of prolonged ultrasound exposure on the fetus have not been studied. So the U.S. Food and Drug
Administration (FDA) does not recommend fetal ultrasound for nonmedical
reasons. Examples are finding out the sex of the fetus or getting a keepsake image.

Three-dimensional (3-D) fetal ultrasound is being
tested for use in finding fetal abnormalities. It is not yet widely
available.

Doppler ultrasound (or duplex scanning) uses reflected
sound waves to estimate the speed and direction of blood as it flows to the
placenta and within the fetus. For more information, see the topic
Doppler Ultrasound.

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